1. Field of the Invention
This invention relates to transport mechanisms for rapidly moving and positioning semiconductor wafers. More specifically, this invention relates to methods and devices for damping vibrations in a handling arm used in such a transport mechanism.
2. Description of Related Art
In modern high speed semiconductor manufacturing operations semiconductor wafers are moved into position for processing with an automated transport mechanism. The transport mechanism uses a handling arm to pick up the wafer and move it into the desired position. One end of the handling arm is connected to the driving portion of the transport mechanism and the other end holds the wafer as it is moved.
One limitation on the speed of processing is the speed with which the handling arm can position and remove the wafer from the processing station. The rapid motion necessary to achieve high speed operation excites vibrations in the handling arm. These vibrations must be allowed to dissipate at least partially before the wafer can be picked up or set down. If the vibrations are not allowed to dissipate sufficiently, positioning accuracy deteriorates. In addition, excess vibration results in particle generation due to impacts between the arm and wafer. This introduces contaminants into the processing chamber.
Existing semiconductor wafer handling arms are not provided with vibration dampers due to the difficulty of finding vibration absorbing materials that are suitable for use in semiconductor processing environments. Semiconductor processing environments are typically characterized by wide pressure and temperature ranges and normally have very low contaminant requirements imposed upon them.
Materials commonly used in other applications to absorb vibrations outgas at low pressures. This creates a source of contaminants that is unacceptable in the ultra-lean environment needed for semiconductor wafer processing. In addition, the damping properties of conventional damping materials vary significantly across the temperature range required to process wafers. This makes them a poor choice for use in such an environment.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a vibration damper for a handling arm that does not use conventional vibration damping materials with their associated contaminant risk and which provides vibration damping for the handling arm over a wide range of processing environment temperatures.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.